Police in Spain say they have arrested three members of online activist gathering Anonymous, who were allegedly involved in attacking Sony’s PlayStation Network, among other targets.

According to the official Twitter account of the country’s national force, the arrests follow an alleged plot to attack Spain’s Central Electoral Board website. The force has posted a screenshot of IRC chatlogs supposedly detailing plans to attack websites including the police’s own site.

The police claim that the detainees aren’t just have-a-go script kiddies, stating that they “have the capacity to make decisions and direct attacks,” and were also involved in a recent attack on the PlayStation Network, as well as action against the governments of Egypt; Chile; Iran; Colombia and Chile, among other targets. (UPDATE:To clarify, this particular hack is believed to be one in which Anonymous-related files were found on Sony servers, not the LulzSec hack which led to the network being offline for several weeks.)

The arrests, in the cities of Barcelona, Alicante and Almeria, follow a recent declaration from NATO that Anonymous is considered a threat which would be “infiltrated” and “persecuted.” The online collective’s response warned NATO “Do not make the mistake of believing you can behead a headless snake. If you slice off one head of Hydra, ten more heads will grow in its place. If you cut down one Anon, ten more will join us purely out of anger at your trampling of dissent.”

It seems that we’re in for many more clashes between the powers that be and online activists and hackers, as the profile of such groups seems to increase with each passing week.

UPDATE: The Spanish police Twitter account has posted this image of an officer posing with one of Anonymous’ famous ‘V for Vendetta’ masks at a press conference today. It’s not clear if this was seized during the arrests or not, but he clearly looks pleased with himself.